Seriously this ring does exist in the multiverse and the science(and we all believe in Science) say so as fictional realism. If he does hold that one ring to rule them all, we are doomed.
Fictional realism is the view that because all universes exist, fictional characters exist (including constructed universes) as well. There are fictional entities, in the same sense in which, setting aside philosophical disputes, there are people, Mondays, numbers and planets.